Strapped magnetron



Patented Apr. 14, 1953 STRAPPED MAGNETRON Albert M. Clogston, Melrose, Mass., assignor, by mesne assignments, to the United States of America as represented by the Secretary of War Application March 1, 1946, Serial No. 651,302

i Claims.

This invention relates to electron discharge devices, and particularly to an improved method of strapping magnetrons.

The conventional magnetron structure includes a number of chambers, or resonant cavities, symmetrically disposed within the anode ring. A number of modes of oscillation are possible, usually being one less than the number of cavities present. It is desirable, however, that oscillation be restricted to as iew widely separated modes as possible, so that all the output power may be concentrated in the frequency range due to this mode, and the tuning may be as sharp as possible.

This aim is achieved by strapping or connecting certain of the resonant cavities together. Conventionally, the strapping takes the form of annular members disposed concentrically with the anode ring and connecting alternate anode segments together. The anode segments are those portions of the anode structure extending radially inward from the anode ring to constitute the walls of the resonant cavities.

These annular members are disposed as near to the inner circumference oi' the anode structure as is convenient, and may be on one or both ends of the anode.

The most effective results are obtained when the impedance path presented by the strapping rings is a minimum. For this reason the straps are commonly made as heavy as possible relative to the rest of the structure; usually two rings are concentrically disposed on the same end of the anode, each ring being brazed to alternate anode segments, and such double strapping is duplicated at the opposite end of the anode.

The location of two concentric rings close together tends to increase the capacitance of the system, with consequent reduction of the impedance. but is limited by the spacing which :must be maintained to avoid iiashovers.

The present invention contemplates heavier strapping, hence greater mode separation, with a system having substantially the same dimensions as the conventional double ring strapping, by using an inner ring almost completely enclosed by an outer strap. This reduces the impedance by lowering the inductance instead of by increasing the capacitance.

The invention may be better understood by reference to the drawing, in which:

Fig. 1 represents a double strapped magnetron anode;

Fig. 2 is a fragmentary view partially in section taken diametrically across a magnetron formed in accordance with this invention;

Fig. 3 is a fragmentary cross-sectional view of the improved strapping arrangement, taken as indicated by line 3-3 of Fig. 2; and

Fig. 4 is a fragmentary cross-sectional view of the improved strapping arrangement, taken as indicated by line 4-4 of Fig. 2.

Referring now to Fig. 1 oi the drawing, I indicates a magnetron anode having a plurality of radially disposed vanes alternately designated by the numerals 2 and 4, between which are resonant cavities 5. An annular strap 6 is disposed adjacent the inner ends of the vanes, and secured, as by brazing, to those numbered 2. A second annular strap 'I is disposed concentrically within strap 6, and is secured to the alternate vanes 4. The alternate vanes 4 are cut away at 9 so that there will be no contact with the annular strap 6, while vanes 2 are similarly cut away at I0 to clear strap 1.

Between straps 6 and I capacitance is added to the circuit, which reduces the impedance and promotes mode separation. To make the increase in capacitance a maximum, these straps must be made as deep as possible, and located as closely together as is permissible in view of the voltages involved. The practical limitations on these two factors substantially define the mode separation obtainable by such means.

In Figs. 2, 3 and 4 is illustrated a preferred version of this invention. An outer or tunnel shaped strap I5 is set into snugly iitting recesses I6 in alternate vanes I 8. Intermediately alternate vanes I9 are recessed at 20 to provide adequate clearance for strap I5. A second tunnel shaped strap II is set in recesses I4 in alternate vanes I9, intermediate vanes I8 being recessed at I1 to provide clearance for strap II. Concentrically within the tunnel strap I 5 is disposed a conventional ring strap 2I arranged to be connected to each of the intermediate alternate vanes I9, but spaced from the alternate vanes I8. A similar strap I3 is connected to vanes I8 but spaced from vanes I9. At each juncture of vanes and ring or tunnel straps, a iirm connection is made by the usual means such as brazing or sweating in a silver solder.

It will be observed in the drawing that opposite connections of vanes and straps are used at the opposite ends of the anode structure. For example, as seen in Fig. 4, whereas the upper end of alternate vane I8 is connected to tunnel shaped strap I5, the lower end is connected to ring strap I3. Likewise, as seen in Fig. 3. where the upper end of intermediate alternate vane I9 is connected to inner or ring strap 2l, the lower end is joined to tunnel shaped strap Il. It will be obvious to those skilled in the art that the strapping may be restricted to one end if desired.

The effect of the arrangement of this invention istoreduce the inductance ofthe strapping systempwhile maintaining the-'saine separation between the straps and substantially the same strap depth. Hence the impedance is reduced.

"throughoutits entire length within said vtunnelsh'apedrmember vand connected to those'of said conducting vWallsnot )joined to said tunnelshaped member.

' 2. A magnetron anode having a "plurality Aof .cavity resonators separated `by Vdividingwalls, i means comprising an'annular vconductor having a tunnel-shaped cross-section throughout its en- *tire'length and disposedadjacent the inner pe- "ripheral -lcoundary'of `said resonators and `connected to alternate dividing walls thereof, and an annular strap A'disposedl throughout its entire 4 length within said tunnel-like conductor and joined to those of said dividing walls not connected to said tunnel-like conductor.

3. A magnetron anode having a plurality of cavity resonators separated by conducting walls, an inner strapping conductor joined to alternate ones. of said conducting walls, andvan outer 'strapping conductorzenclosingfsa'idfinner conductor throughout its entire length, and joined yto those of said conducting walls not engaged by said inner conductor.

" 4. YA magnetron anode as set forth in claim 3,

whereinesaid conductors are positioned in the upperpo'rtion of Vsaid walls, and further includlingle secondinner strapping conductor, and a second outer strapping conductor enclosing said second Vinner conductor throughout its entire length, said second outer conductor being joined to the same walls as Ysaid iirst mentioned inner conductor, and said second inner conductor. being joined tothe samewalls: as saidrstmentioned outerconductor, said second 'conductors being positioned in the lower portion"ofi,sad

' walls.

, ALBERT. M. 'CLOGSTON References Cited in the'le of thisfpatent UNITED STATESYPTENTS Number Name 'l Date 2,418,117 Hale'etal .."|Apr. 1, y1947 2,443,445 VDonal Jr; et al. rJune 15, 1948 2,447,537 Ronci Aug. 24, 1948 

